Although a silica fine powder has been added as a filler to a semiconductor resin-sealing agent in order to improve a fluidity and a burr-proof property, this invention relates to an amorphous spherical silica particle suitable as this filler, and its production process. Moreover, although it is known that a blocking is prevented by adding the filler to a plastic film or sheet to form the fine irregularity on the surface of the film to decrease a contact area, the amorphous fine silica particle of this invention is also suitable as this filler.
Furthermore, an outer additional agent has been used to improve the fluidity, heat resistance, and long-term preservation of the toner for the electronic photograph, and said agent has also been used to control an electrification property, a cleaning characteristic, an adhesion property on a carrier or a surface of the photo conductor, and degradation behavior of a development material. In addition, an inner additional agent has been used to improve a durability of the toner for the electronic photograph, and to raise a durability of the surface protection layer of the photo conductor of the electronic photograph, which is loaded electrically or mechanically. This invention relates to the suitable amorphous spherical silica particle as a material used for the purpose of the improvement of the fluidity and the control of the electrification property, the improvement of the heat resistance and the long-term preservation, the control of a cleaning characteristic and adhesion property to the surface of the carrier or the photo conductor, and the control of the degradation of the development agent, by appending to the outside of the toner for the electronic photograph. Moreover, said silica particle is also used for the purpose of the durability improvement, by appending to the inside of the toner for the electronic photograph, and is also used in order to decrease the contact area to improve the durability, by forming the fine irregularity on the surface protection layer of the photo conductor of the electronic photograph, which is loaded by the electric or mechanical load.
Regarding the silica filler used as the semiconductor resin-sealing agent, it is good that said silica filler has high purity as much as possible to have a true spherical form, and has a suitable particle size distribution. Moreover, in order to have a high filling and the high fluidity, it is effective that said silica filler can be filled up in the fine space between these silica particles, and be improved the sliding between these particles. Therefore, the particle having 0.1–1 μm of an average diameter and 5–30 m2/g of a specific surface area by BET (hereafter it is said the specific surface area), has been used in general. Moreover, as the outer additional agent of the toner for the electronic photograph, the silica particle, or a titanium oxide particle, etc., having 0.006–0.040 μm of the average particle diameter, has been used now for the purpose of the improvement of the fluidity and the control of the electrification in general. In addition, as the inner additional agent, the silica particle having 0.005–0.040 μm of the average particle diameter, has been used, and is required that said silica particle has a sharp particle size distribution, in order to correspond to a high speed, a clear picture and the control of the degradation behavior of the development material etc. Furthermore, although the silica particle having 0.005–0.150 μm of the average particle diameter, has been used in order to raise the durability of the surface protection layer or the electric charge transportation layer of the photo conductor of the electronic photographic, the wet silica and the silica gel made by using sodium silicate as a raw material, have the problem that the content of alkaline metals, such as soda, is high. Therefore, the fine silica particle with few amounts of alkaline metals, having the suitable particle size, is required instead of said wet silica and silica gel. Moreover, regarding the conventional wet silica and silica gel made by using sodium silicate as the raw material, since an alkaline metal oxide, such as soda, is intermixed as an impurity, said silica has the fault, in which the electrification is low and a standup of the electrification is late, and also has a problem in the durability. Furthermore, the conventional silica powder used as the additional agent of the material of the electronic photograph has a problem that the particle size distribution is broad, and the average particle diameter is too small.
By the way, by the conventional sol-gel method, it is difficult to make a particle of less than 1 μm, and it is also difficult to obtain the fine silica particle having the particle size, which is preferable as such a material of the filler. Moreover, by the sol-gel method, even if the particle of less than 1 μm is made, growth and sintering of particles each other will arise at the time of burning to make a stable silica particle, so that the silica particle, which can be isodispersed, cannot be obtained while keeping said particle size stably. Moreover, the fine particle of the reaction products by sol-gel method, which is inadequate burning, has a problem that silanol groups and organic materials are remained too much and the compound, which is kneaded and filled up with said particle, generates gases at the time of injection molding or fabrication, so that said particle cannot be used for the filler for the semiconductor resin-sealing agent.
On the other hand, regarding the titanium dioxide particle, it is known that the process, in which the crystalline particle of more than 0.1 μm is made by using a titanium tetrachloride as the raw material to be oxidized directly under high temperature with oxygen gas. However, regarding a direct oxidation reaction of silica, since said reaction has to do under more high temperature than titanium dioxide, and the melting point (1730° C.) and the boiling point (2230° C.) are closed, so that the growth of the particle is not enough, and it is easy to become an ultra fine particle of less than 0.1 μm. Moreover, the productivity is also low. Therefore, it is also difficult to obtain the silica particle having the preferable particle size as the material of the filler by this method.
In addition, the process, in which a metallic silicon powder is lit in an atmosphere containing oxygen to form a flame to be done oxidization combustion continuously, has a problem that the purity of the made silica powder is low. Regarding the silica fine powder used for the semiconductor resin-sealing agent, the high purity is required, specifically, it is needed that there are as much as possible few uranium contents, so that a radiation error may not be occurred. However, since it is difficult to refine the metallic silicon, the silica fine powder having high purity cannot be made at low cost, by the oxidation combustion method using said metal silicon as the raw material.